Many different types of rotary devices have been suggested in the past and have been covered by a large number of patents. Only a relatively small number of these have been thoroughly tested. Many rotary devices such as engines are of interest on paper, but practical difficulties arise when prototypes are constructed. In the field of rotary engines, the best known is the Wankel engine that has been in volume production in Mazda automobiles. Even this engine has had considerable difficulties with proper sealing of the rotors, although such problems have been large overcome.
Another type of rotary engine is referred to herein as the “axial vane type”. This type of engine has a cylindrical rotor located within the cylindrical chamber in a stator. A plurality of blade-like vanes extends slideably through the rotor, parallel to the axis of rotation. There are undulating, parallel cam surfaces on each side of the rotor. High portions of the cam surface on one side align with low portions of the cam surface on the other side.
Rotary engines and other rotary devices such as pumps, compressors and expanders, for example, offer many potential advantages including high efficiency, simple construction and lightweight. However, while the theoretical possibilities of such devices have been suggested in the past, many practical difficulties have inhibited their development beyond the stage of the working prototype. As mentioned above, axial vane rotary devices typically employ solid, generally rectangularly shaped vanes that axially slide on the rotor in response to urging by undulating cam surfaces formed on the end walls of the housing that contains the rotor. The cam surfaces are opposed in that high points on the cam surface on one side of the housing are opposed to low point on the cam surface of the opposite end wall. Only one of the outer edges of the vanes will normally contact a cam surface at a time while the opposite edge is spaced slightly from the cam surface thus providing a gap for leakage of compressed fluid. Likewise during operation, centrifugal force may cause the vanes to lift creating a gap between the inner edges of the vanes and the stationary inner housing in which the rotor drive shaft is housed. Some earlier publications fail to disclose any practical system of seals between the rotor, vanes and stator. In the absence of good sealing the efficiency of the rotary devices is substantially reduced especially in the case of pumps, expanders and compressors.
In an attempt to overcome the sealing problems encountered in axial vane rotary devices some designs of such devices includes the vanes that further include spring members to normally urge the vanes are. Examples of such devices are found in U.S. Pat. No. 22,955, granted Feb. 15, 1859 and U.S. Pat. No. 3,489,126, granted Jan. 13, 1970. Despite these designs, leakage continues to be a problem, particularly between the inner edge of a vane and the inner housing of the rotor in which the rotor drive shaft is contained.
Some of the leakage problems caused by poor sealing have been overcome by an improved axial vane device as described in U.S. Pat. Nos. 5,509,793, 5,551,853 and 5,429,084 to Cherry, et al. The axial vane devices of the type described in these patents are used as pumps, expanders and compressors.
However, sealing the axial vanes in an axial vane rotary device adds substantially to the complexity and cost of manufacture and can result in high maintenance costs. Accordingly, it would be highly desirable to provide a vane design for an axial vane rotary device that provides improved sealing and device efficiency while allowing for the reduction of the complexity and number of seals required and resulting reduction of manufacturing cost.